You did that from scratch? Clever and well executed.
 

You did that from scratch? Clever and well executed.

Ok, thanks. Is a tri-link set up suitable for turbo aplications 350- 400rwhp? Im concerned that the axle housing might be stressed more than it already was with a tri-link.

What if you replaced the bushings with heim links? Would that provide the needed flexibility in movement?


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you wouldn't be the first to do a tri link @400rwhp

i was thinking that last night, but i think you'd really have to get up in there and make sure. the binding comes from the upper links not being parallel, and kind of short.

the factory fix was to change the mounting point to the axle, and run longer links.

the toyota people do this with the traction brackets https://technotoytuning.com/toyota/a...s-ae86-corolla

a friend of mine has a fully built hatchi, which is almost the same as a 1st gen, and they lowered the lower link on the axle, so they could lower the car, and then they just run a set of lower links as upper links, and made the panhard adjustable.

What are people using to replace the suspension with a subframe/IRS when not restricted by rules that mandate the solid axle?

I seem to remember a few that had custom or aftermarket IRS and possibly Jaguar rears? What about an FD rear end? Any recommendations?

To the issue of rear suspension mods for 300+H.p., You may want to read the toyota 8" swap thread because these axles are known to go bad at a lower HP than 300. Just saying the 'yota or ford 8.8 may be in your near future.

^^Yeah, the standard 26 spline diff (with torsen) has stood up surprisingly well when ive gone thru a couple of s5 g'boxes and three button clutches, although thats probly just bad driving:blush: - no more burnouts for me lol, so im guessing im on a good thing with the relatively light weight std diff, and reluctant to go tri-link on it if it makes it more vulnerable to twisting forces, but i'll definately be looking into it.



^^ this is pretty much exactly what im toying with the idea of;
extend the lower link mount on the axle, and raise the upper link mount on the chassis, thereby compensating for lowered ride height, and hopefully reducing the amount the pinion wants to hit the floor becuase of the extra leverage of the longer lower mounts.

The other hare-brain idea im playing with is moving the watts mount lower on the diff, and lengthening the short side of the pivot piece( excuse the incorrect terminology) so that the pivot piece is actually symetrical (will keep the standard enequal length arms tho).

I'll probably end up just using a panhard bar tho, too much stuffing about trying to polish a turd.

Ok sorry guys for polluting such a great thread with so much jibberish.
Mods, feel free to clean up after me. next time i should be able to put up some pics of what ive been up to.

Why would you even want an IRS? Solid axle is superior.

I'm toying with the idea of moving to an E30 BMW, but part of the plan is replacing the IRS with a stick axle because they just work better.

My experience is that the housing is the weak point. When you keep the stock 4-link, the housing twists and the pinion angle keeps going up. My assumption is that this is due to the upper link bind being resolved by the housing itself twisting, and torque loading when accelerating out of a corner puts an additional strain on one side.

3-linking solves that issue, but then you get into the issue of the axle housing developing more and more toe-in, which eats axle bearings, and then the middle splits open like an egg and you eat the front pinion bearing after you drive 150 miles with no fluid in the diff...

:lol::lol::lol: I'm not sure what you mean with that kind of general statement. I'm not a big fan of the E30 trailing links either but they still do pretty well and there are other options like a Ford 8.8 IRS or multilink IRS. I think someone has swapped in an E90 rear. (referring to BMW's not Mazda's)

Solid axles have some advantages including cost and less complexity, and can be a good choice for certain very specific applications, like drag racing. However that technology was passed by 50+ years ago. When you get your E30 converted let me know and we can meet for a few laps at the Glen or mid Ohio. :icon_tup:

The old IRS vs. Live Axle debate has raged for decades. After some research on this while designing my Toyota 8 setup (https://www.rx7club.com/build-thread...a-8-fb-992844/), most designers agree that live axle geometry benefits from long control arms -- whether it's a tri-link setup like mine or a torque arm arrangement. Packaging that stuff in a production vehicle is difficult.

That said, the current Mustang rear end seems to work fairly well. It uses a tri-link/Panhard with a very short upper link (generally undesirable for performance, but necessary for rear occcupant room). In recent road race comparisons with current generation Camaros and Challengers that both have IRS, the Mustang fairs very well.

I think my car would corner slightly better with a little negative camber in the rear. While this can be done with a live axle, I'm told it's best done with full floater hubs and crowned axle shafts, which aren't a production solution and aren't in my budget either.

I don't think there's any inherent issue with a tri link and high horsepower. Trans-Am cars ran them for years with good success. I was personally concerned with the bent upper arm used in setups that don't alter the tunnel area, so I modified the tunnel in my car so I could use a straight one.

And that's the only reason for IRS - it requires less interior volume for the same amount of suspension travel, and it's easier to isolate NVH.

Mind you, I'm competing on "unimproved surfaces". (Most will admit that on smooth tracks, there's no real difference between IRS and solid) At Nationals, my cars was quicker than all of the Miatas, all of the BMWs, most of the front-drives, AND most of the all wheel drives. Sadly it wasn't with ME actually driving :) but solid axle is just plain superior as a performance item. There are huge benefits you can get with respect to planting the rear tires that are not available to you if you decouple axle torque from suspension motion.

Why were some of the front wheel drive cars quicker?

Not that this could be done to this extent on a street car, but I am sure with some careful design, it could be done on a street car!

Inverted triangulated 4-link:

http://www.lamanracing.com/wp-conten...7/img_0778.jpg

As a rule, FWD is much quicker than RWD and often quicker than AWD, at rallycross.

Some of the fastest times posted at Nationals, IIRC, were in a bone stock Mazda2.

FWD is much more fragile, much more prone to debeading tires and breaking CVs, so I stopped running them.

I see. I assumed autocross. I didn't really pay attention to the "unimproved surfaces" part.

Sorry for the threadjack.

http://www.flickr.com/photos/rk970/8080617330/http://www.flickr.com/photos/rk970/8080617330/ by http://www.flickr.com/people/rk970/, on Flickr

http://www.flickr.com/photos/rk970/8080617406/http://www.flickr.com/photos/rk970/8080617406/ by http://www.flickr.com/people/rk970/, on Flickr

Anti squat is at about 55%. Upper third link is off set the to the right 4.5" (helps to stop lifting the right rear under acceleration) Panhard is close to the bottom of the diff housing..
I have a question.. Since I have converted/built a three link rear suspension.. is it really necessary to run the huge 1 1/8" front sway bar..? 225 in/lbs in the front and 175 in/lbs in the rear.. 3/4" suspension drop from stock height with 5/8" spacer between the steering arm and strut..
This is for a street car not a track weapon..
Rk

I will have to do some calcs to see if your spring rates are good with those numbers!
However, I would highly recommend adding some gussets or something similar around where the bottom bars connect to the center of the diff. The bar welded alone will most likely fail as some point! If you can send me a picture looking at the diff from the back, I can put some gussets on there that will work!

For what it's worth:

The problem I had:

Attachment 694984

Note that I'd already welded one crack shut. A new cracked opened up right by it, signifying that there's got to be a strong stretching force right there.

Solution:

Attachment 694985

Simple, effective.

Still does not answer the question about the front sway bar...

the E30 just looks like it has IRS, it doesn't actually WORK like it has IRS, if there is a swaybar on it, its just a solid axle with lots of negative camber.

last weekend race

was having good race

until i snap my upper tri link

hard to imagine i just rip it apart

i know with my 13BPP n hoosier bias slick i might have some problem

but never know will happend in this way !!!

http://i81.servimg.com/u/f81/17/73/72/09/img_3410.jpg

Wow. Do you run a cover over that slit at all, or is it open space to the ground?

I know that at least one of the guys who would three-link or equal length four-length the car, would use shifter boots to seal the hole.

good idea. I have 8x 1/2" aircraft strength heims and 4x adjustable equal length arms on order, and have been trying to think of how to seal the upper inner joints/mounts from the outside.


Im choosing to do the vintage Mazda race car design of custom upper mounts inboard , equal length 4 links and heim'd watts with a urethane bushing on the pivot mount (ill just hide the new upper mounts under the storage bins ;) )

put a Go pro hero3 on rear suspension ... look like i can get some stiff spring at back now !!

That's really weird, it says I posted this Oct. 4, 2013.

October 4th, I was in Tulsa at the SCCA Rallycross National Championship, not posting to RX-7 Club. And, furthermore, at 1:45am I was outside the hotel BS'ing with friends, since I was outside from about midnight to 2:30am.

Weird...

What size and brand is that heim? Interesting failure. In my experience, the brackets fail but not the heim.

i don't know about your settings but the default time setting is like Greenwich mean time, which is ~8hours different. for instance it is 10:34am here, and posting time says 5:34pm.

"All times are GMT -4" and current time is same as mine.

So that was posted at 1:45am "San Dimas time" which is actually 45 after midnight Tulsa time.

The thing is, I remember posting that, a looong time ago.

I get a kick out of the muffler hanger as a side load g-force meter..

another shot

i think my upper link move too much (L/R) wise

hows every one's idea

I think that much lateral movement is fine in a road car but a little much for a Race-car. Just my opinion and not backed by any actual facts. :)

I see remote reservoirs. Which shocks are you using?

Local brand( taiwan(Which I will never use it again on
Any of my race car

JRZ double adjusable

that is probably the problem. the rod end is designed to move side to side, so until it binds it should be totally fine.

not to get too far into it, but the US made parts have quality control standards and are usually made out of the material they say they are

Aurora brand heims and bearings all the way

I use Aurora too. The Teflon-lined versions have done track and street duty for me while remaining silent (no clunking).

I know it's loud while on track; so you probably couldn't hear the failure.

But, I suspect you felt it immediately. Do you recall if it was under acceleration or deceleration and/or over bumpy section of the track?

U don't need to hear it or feel it
Because car was not driving able

N hearing ur driving shaft bang on tunal is not fun

I think is the corner exit meaning I am on Gas

I get about two days worth of use from Summit's Black Magic rod ends (3/4" thread 5/8" hole) before they start to clunk.

Rod ends can move side to side but it still must not bottom out in the bracket. My 3-link was designed around the width of a stock rear upper/lower link bushing, so I have spacers on the sides of the rod end. The spacers are not equal in thickness, either... I was playing around with angling the upper link to compensate for driveshaft torque-over. No lifting the right tire under acceleration for me!

My .02 is that it's impossible and undesirable to eliminate all lateral movement. Without using reinforcements much larger than needed; the chassis, frame rails/unibody, roll cage; etc. will always flex under load.

After looking at both of your vids; my concern would be the width of the bracket where the heim failed. If it's too narrow and/or too tight it will bind and fail. I believe it was MustangHammer ( my apologies -- it was peejay) who commented about using spacers on either side of the heim to take up the slack. This would allow the lateral movement without the binding and undue stress.

The only other logical cause for the failure would be massive amounts of torque being applied during acceleration/deceleration cause you're making too much power or have too much braking capabilities...;-) Nah, that couldn't be it.

Good luck with the fix! Looking forward to a follow-up post after it's figured out.

Anoter Rod end fail..........................and is at final lap of race... That really sucks

luckyly i caught all the fail on the tape


that was my last race of the season

i think i might change the Tri link design to Lotus link or 4-link design

Use a heavier rod. That size is just too light weight for the track.

agreed, that rod-end looks way too tiny (maybe a 1/2" or 12.7mm?). Also, you could be having binding issues by running such a narrow chassis mount bracket. I would try a larger, quality, heavier duty rod-end, like 5/8 or 3/4 (16mm or 19mm) and make the chassis mount wider and run some "high offset" spacers to allow for more useable articulation

Your initial thought was that the failure occurred under power; the last video corroborates it. It failed right when you applied the shock load of an upshift. Under accel load, the lower links will be in compression, and the upper is likely to be in tension due to the reaction torque from the rear tire traction. That would explain your tensile failure.

I have a similar setup with a narrow clevis. If you have a heim-jointed panhard rod or Watts link, I doubt there's enough lateral movement to put that upper link into a bind. My upper link doesn't bind, and it has plenty of unneeded additional lateral range (I can move the rear end of the link about 8" from side-to-side).

My upper link does use 5/8" Aurora AM rod ends.

I would try up-sizing, as elron suggested, and/or getting a higher strength heim joint before making any drastic suspension changes.

Question,
I'm using the old re speed coil perch parts for my front. The handling has continued to be worse and worse. It almost feels like one side is blown out, when I go over speed bumps the car feels stiff on one side and squishy on the other. What parts need replaced? Iirc I have white tokico all 4 corners, 350 or 375 Springs front, 175 Springs rear

Also I found that the bushings in the stock rear end links are very worn & causing the car to make a bunch of rattle sounds, is replacing those with Mazda oe parts a good decision, or is there a better aftermarket part I don't know about